Method for producing a plastic composite element

ABSTRACT

A method for producing a plastic composite element, in particular an interior lining element for a motor vehicle, and such a plastic composite element.  
     The present invention relates to a method for producing a plastic composite element ( 1 ), in particular as an interior lining element for a motor vehicle, with an outer covering ( 2 ) being lined with a foamable plastic, characterized in that the outer covering ( 2 ) is lined at least partially with a flexible foam ( 3 ), that the flexible foam ( 3 ) is subsequently lined with a rigid foam ( 5 ) with a separating means being placed thereinbetween, and that a shaped part ( 4 ) which can be prefabricated is used as the separating means which by virtue of the mechanical properties of its material and/or its shape prevents the rigid foam ( 5 ) from penetrating the flexible foam ( 3 ) and/or prevents a deformation of the outer covering ( 2 ), and such a plastic composite element ( 2 ).

[0001] The present invention relates to a method for producing a plasticcomposite element, in particular an interior lining element for a motorvehicle, according to the preamble of claim 1, and such a plasticcomposite element.

[0002] Known are methods for producing a plastic composite elementwherein an outer covering is lined with a foamable plastic. When acorrespondingly rigid foam is used, a further area, for instance aninterior trim for a vehicular door, can be shaped simultaneously withthe lining and connected to the outer covering. Further decorationelements or e.g. loudspeakers of an audio system can be mounted on therigid foam. The rigidity of the rigid foam required in this connectionis however inconsistent with the high demands made on comfort and/orsafety, which necessitate—at least in specific areas of the compositeelement—a soft touch and/or a resilience.

[0003] U.S. Pat. No. 5,851,457 discloses a method according to thepreamble of claim 1 for producing a seat cushion. A layer of thecovering unit is here pressed into a lower mold by the action of avacuum, and the back side thereof is then foamed with a plastic materialto form a foam core. The specific weight of the foam core is 40 to 60kg/m³, corresponding to 0.04 to 0.06 g/cm³. The layered covering unitconsists of the cushion slip, a breathable foam mat, an air-impermeablebarrier layer and an insulating undercoat.

[0004] It is the object of the present invention to provide a method forproducing a plastic composite element and a corresponding plasticcomposite element which overcomes the drawbacks of the prior art, inparticular, with which a plastic composite element can be produced atlow costs that satisfies all demands made on comfort and/or safety.

[0005] A sandwich structure of outer covering/flexible foam/rigid foamwould be desirable in particular in specific areas of the interior trimof a motor vehicle. During foaming of the rigid foam in the foam mold,however, compressive stresses arise in the rigid foam that are so highthat the flexible foam is deformed and that, when the composite elementis removed from the mold, the outer covering and thus the contour,texture, relief and/or decoration of the outer covering are deformed.The invention is therefore to realize, in particular, a sandwichstructure consisting of outer covering/flexible foam/rigid foam withouta deformation of the outer covering impairing the function and/oresthetics of the composite element.

[0006] The object is achieved by the method and the composite elementdefined in the independent patent claims. Special embodiments of theinvention are defined in the subclaims.

[0007] The object is achieved by a method for producing a plasticcomposite element, in particular an interior lining element for a motorvehicle, wherein an outer covering is lined at least partially with aflexible foam which is subsequently lined with a rigid foam with aseparating means being placed thereinbetween, a shaped part which can beprefabricated being used as the separating means which by virtue of themechanical properties of its material and/or its shape prevents therigid foam from penetrating the flexible foam and/or prevents adeformation of the outer covering.

[0008] The use of the term flexible foam is to be understood as adistinction over the rigid foam which is also to be applied, and is toexpress that the flexible foam is more flexible than the rigid foam.Therefore, the flexible foam according to claim 1 also includesso-called semi-rigid foams, such as polyurethane foams having a specificweight of e.g. 0.11 to 1.18 g/m³. The rigidity of the flexible foam canbe adjusted by the mixing ratio of the components, which are normallytwo, and can be adapted to the demands made on the comfort and/or safetyof the respective application, in particular in consideration of theshape of the composite element, the thickness of the flexible foamand/or the thickness and rigidity of the rigid foam.

[0009] The outer covering may consist of a plastic material, e.g. adeep-drawn polyvinyl chloride (PVC), and comprise a relief and/ordecoration on the visible surface. Typical reliefs are e.g. grainedimitation leathers. The outer covering may be a shaped part which can beprefabricated accordingly.

[0010] The separating means between flexible and rigid foam canpreferably be produced by deep drawing, deep-drawn parts of plasticsbeing particularly suited for reasons of costs, e.g. parts made ofacrylic butadiene styrene (ABS), polyvinyl chloride (PVC) or polystyrene(PS). The initial thickness of the shaped part used as the separatingmeans is e.g. between 0.1 and 0.7 mm, depending on the material used andthe shape. A thickness preferred for e.g. for ABS and a standard shapeis 0.3 mm. The separating means prevents a change which is detrimentalto esthetics, haptics, shape and/or safety and arises in the flexiblefoam and/or the outer covering or the composite element due to thecompressive stresses arising during the back-foaming with rigid foam andpossibly becoming visible upon removal of the composite element from themold.

[0011] For lining purposes the outer covering is placed into acorrespondingly formed lower mold and the flexible foam material whichforms the flexible foam is then applied to the back side of the outercovering. Depending on the temperature of the flexible foam material,the shape and the environment, it will take some time, normally a fewseconds, until a foaming and thus, an increase in volume of the flexiblefoam material occurs. Prior to or during foaming of the flexible foammaterial the shaped part is brought into contact with the flexible foammaterial. To this end it is preferably mounted on a correspondinglyshaped upper mold and held in the upper mold, for instance by vacuumapplication at the back side, locking or clamping.

[0012] Upon contact of the shaped part with the flexible foam materialthe shaped part is brought—preferably in the edge portion thereof—intocontact with the outer covering and is connected e.g. by exitingflexible foam material with said material such that a penetration ofrigid foam during subsequent lining with rigid foam is prevented.Preferably, the shaped part is shaped such that a planar or linearcontact or a positive connection with the outer covering is obtained inthe edge portion of said shaped part.

[0013] The costs for the plastic composite element according to theinvention can be reduced further when the outer covering is also adeep-drawn part which can be prefabricated. Almost any reliefs ordecorations can thereby be realized in a simple and reproducible way andwill survive the foaming process with rigid foam without any damage.

[0014] Further advantages, features and details of the invention willbecome apparent from the subclaims and the following description inwhich one embodiment is described in detail with reference to thedrawings. The features indicated in the claims and in the descriptioncan each be essential for the invention, taken either individually or inany desired combination.

[0015]FIG. 1 shows a detail of the production of a plastic compositeelement according to the invention; and

[0016]FIG. 2 shows a cross section through a plastic composite elementaccording to the invention.

[0017]FIG. 1 shows a detail of the production of a plastic compositeelement 1 according to the invention, namely the lining of the outercovering 2 with a flexible foam 3 and the application of a shaped part 4as a separating means between the flexible foam 3 and the rigid foam 5to be applied subsequently. To this end a predeterminable amount of theflexible foam material which after foaming yields a PU semi-rigid foamwith a specific weight between 0.11 and 0.18 g/cm³ is applied to theback side 2 a of the outer covering 2 which is put into a lower mold 6and has previously been produced as a deep-drawn part from PVC, possiblyby using the illustrated lower mold 6, and which is provided on itssurface 2 b with a decoration and/or a relief.

[0018] Subsequently, the upper mold 7, including the mounted shaped part4 which has been produced by deep drawing from an ABS plastic materialwith an initial thickness adapted to the mechanical properties required,and the lower mold 6 are joined, i.e. as long as the flexible foam 3 isfoaming and still deformable. At a temperature of the lower and uppermolds 6, 7 of e.g. about 45° C. and a suitable flexible foam material,the foaming process starts and thus the increase in volume of theflexible foam material after about 10 to 12 seconds after application tothe outer covering 2. Lower and upper molds 6, 7 remain closed until thecomplete hardening of the flexible foam 3. After the mold has beenopened, the composite of outer covering 2/flexible foam 3/shaped part 4is lined in a further step of the method with a rigid foam 5.

[0019] In the illustrated embodiment the shaped part 4 is fixed byvacuum application at the back side to the upper mold 7 which to thisend comprises connection channels 8 between a vacuum chamber 9, whichcan be brought into operative communication with a vacuum pump (notshown) and can be aerated, if necessary, and the mold surface 7 a of theupper mold 7 which is oriented towards the back side 4 a of the shapedpart 4. Alternatively or in addition, the shaped part 4 can also befixed by clamping or locking to the upper mold 7.

[0020]FIG. 2 is a cross-sectional view showing a plastic compositeelement 1 according to the invention. This is in particular an elementof an interior trim for a door of a motor vehicle. The outer covering 2has been prefabricated by deep drawing. On its surface 2 b directed tothe interior of the motor vehicle, it comprises a leather-like textureor graining. In an area of the interior trim of the door which forms aledge of the door window, the outer covering is lined with the flexiblefoam 3. The hardness of the flexible foam 3 and the thickness of theflexible foam layer are adapted to the respective application, inparticular to the demands made on comfort and/or security.

[0021] The flexible foam 3 is lined with the rigid foam 5 withintermediate placement of the shaped part 4 which has also beenprefabricated by deep drawing and consists of an ABS plastic materialhaving an initial thickness of 0.3 mm. The shaped part 4 is connected onits edge portions in planar contact with the outer covering 2 and by theflexible foam 3 to said covering, so that the rigid foam 5 is reliablyprevented from penetrating the area of the flexible foam 3 between theouter covering 2 and the shaped part 4. Outside the shaped part 4 and inparticular in an area in which the demands made on comfort and/or safetydo not require a flexible foam 3, the rigid foam 5 can come into directcontact with the outer covering 2 and directly line said covering.

1. A method for producing a plastic composite element (1), in particularas an interior lining element for a motor vehicle, with an outercovering (2) being lined with a foamable plastic, characterized in thatsaid outer covering (2) is lined at least partially with a flexible foam(3), that said flexible foam (3) is subsequently lined with a rigid foam(5), with a separating means being placed thereinbetween, and that ashaped part (4) which can be prefabricated is used as said separatingmeans which by virtue of the mechanical properties of its materialand/or its shape prevents said rigid foam (5) from penetrating saidflexible foam (3) and/or prevents a deformation of said outer covering(2).
 2. The method according to claim 1, characterized in that saidshaped part (4) is produced by deep drawing.
 3. The method according toclaim 2, characterized in that said shaped part (4) is made of plastics,for instance acrylic butadiene styrene, polyvinyl chloride orpolystyrene with an initial thickness of 0.1 to 0.7 mm, preferably 0.25to 0.4 mm.
 4. The method according to any one of claims 1 to 3,characterized in that during lining of said outer covering (2), aflexible foam material forming said flexible foam (3) is applied to aback side (2 a) of said outer covering (2) which is laid into a lowermold (6) and subsequently, before or during foaming of said flexiblefoam material, said shaped part (4) which is mounted on an upper mold(7) is brought into contact with said flexible foam material.
 5. Themethod according to any one of claims 1 to 4, characterized in that saidshaped part (4), preferably in the edge portion thereof, is brought intocontact with said outer covering (2) and connected thereto.
 6. Themethod according to any one of claims 1 to 5, characterized in that saidsoft flexible foam (3) is a polyurethane foam having a specific weightfrom 0.11 to 0.18 g/cm³.
 7. A plastic composite element (1), inparticular an interior lining element for a motor vehicle, with an outercovering (2) being lined with a foamable plastic, characterized in thatsaid outer covering (2) is lined at least partially with a flexible foam(3), that said flexible foam (3) is lined with a rigid foam (5) with aseparating means being placed thereinbetween, that said separating meansis a shaped part (4) which can be prefabricated and which by virtue ofthe mechanical properties of its material and/or its shape prevents saidouter covering (2) from being deformed by said rigid foam (5).
 8. Theplastic composite element (1) according to claim 7, characterized inthat said outer covering (2) is a deep-drawn part which can beprefabricated.
 9. The plastic composite element (1) according to claim 7or 8, characterized in that said outer covering (2) is made of plastics,for instance of polyvinyl chloride.